High doses of blood pressure drugs needed in winter

By Matías A. Loewy

BUENOS AIRES (Reuters Health) - Some hypertensive patients may need to take higher doses of medication during winter months to control their high blood pressure, a Mexican study suggests. The findings were presented here at the XV Argentine Congress of Hypertension.

Dr. Salvador Fonseca-Reyes and José Parra-Carrillo, of the University of Guadalajara's Cardiovascular Research Unit, studied 100 hypertensive patients whose blood pressure was measured in their hospital office once in every season. They found that only 32 percent of patients had their blood pressure controlled in winter months, compared with about 50 percent in spring and summer.

"If patients had shown previously to have their blood pressure controlled, it might be advisable to increase temporarily the dose of drugs during the cold months," Dr. Fonseca-Reyes told Reuters Health.

In Guadalajara, where the study took place, temperatures can range from a low of 6 degrees C (42.8 F) in winter to a high of 34 degrees C (93.2 F) in summer. The researchers found that average blood pressure was higher in autumn (142.9/83.5 mm Hg) and winter (141.2/84.1 mm Hg) than in spring (133.6/80.7 mm Hg) or summer (137/80.8 mm Hg).

According to Dr. Fonseca-Reyes, the seasonal effect on blood pressure could not be attributed to different adherence to pharmacological treatment or weight gain in cold months. "Causes have yet to be found," he said.

If the "winter effect" is confirmed, he advised, doctors should factor that into decision making. "Perhaps you have to wait (instead of changing or adding drugs). Or increase the dose of the drugs until winter ends," Dr. Fonseca-Reyes suggested.